flat snail? nudibranch?

[rupnow]

On my TBS rocks there are several small animals (like a flat snail) that look exactly like the rock. They are carpeted with algea and one would never see them except that they move. Are these good or bad? They look a little like one of the pictures of nudibracnches on the TBS website. Should I remove them?

 

[Ikaria]

Are you sure it's not just a limpet? I've noticed a few on my rock.

 

[rupnow]

Thanks Ikaria. I'm a novice so all of the animals are new to me. I'll do a bit more searching to see if I can find an image of one like this. The closest picture I could find was in the drop-down menu of organisms on the TBS site (76: Phyllidiidae: Nudibranch (Unknown)). It's pretty cool since its all decorated with sand and algae. I'll try to take a picture and post to my gallery. I heard nudibranches can be destructive but, for now, I'll leave them be unless I see them misbehaving.